Trench structures have several uses in semiconductor device technology. Such uses include isolation structures, control electrode structures, capacitor structures, charge-compensated super-junction structures, and buried contact structures among others. Trench structures typically are filled and/or lined with materials such as dielectrics, semi-conductive materials, conductive materials or combinations of such materials. These materials or fill materials are a common source of problems in trench structures.
For example, fill materials often cause high levels of stress within the device structure, which can in turn lead to defect formation and ultimately, device failure. Specifically, the defects create unwanted parasitic current leakage paths. Also, in some structures, silicon or polysilicon/oxide fill materials create parasitic MOS devices that can impair device performance. In addition, thermally generated carriers (electrons and holes) in semiconductor fill materials can create undesirable electric fields that can compromise breakdown or stand-off voltage of trench structures. Further, methods used to form present trench structures often incorporate contaminants in core regions of the trenches during processing. This contamination also can lead to defect formation and general impairment of device performance.
Accordingly, structures and processes are needed to effectively plug or seal trench structures while reducing stress, defects, parasitic structures, and contamination.
For simplicity and clarity of illustration, elements in the figures are not necessarily drawn to scale, and the same reference numbers in different figures denote generally the same elements. Additionally, descriptions and details of well-known steps and elements may be omitted for simplicity of the description. As used herein current-carrying electrode means an element of a device that carries current through the device such as a source or a drain of an MOS transistor or an emitter or a collector of a bipolar transistor or a cathode or anode of a diode, and a control electrode means an element of the device that controls current through the device such as a gate of a MOS transistor or a base of a bipolar transistor. Although the devices are explained herein as certain N-channel devices, a person of ordinary skill in the art will appreciate that P-channel devices and complementary devices are also possible in accordance with the present invention. For clarity of the drawings, doped regions of device structures are illustrated as having generally straight-line edges and precise angular corners. However, those skilled in the art understand that due to the diffusion and activation of dopants, the edges of doped regions are generally not straight lines and the corners are not precise angles.
In addition, structures of the present description may embody either a cellular base design (where the body regions are a plurality of distinct and separate cellular regions) or a single base design (where the body region is a single region formed in an elongated pattern, typically in a serpentine pattern or a central portion with connected appendages). However, one embodiment of the present description will be described as a cellular base design throughout the description for ease of understanding. It should be understood that it is intended that the present disclosure encompass both a cellular base design and a single base design.